New and Improved Encoded copie_scr.sh Script

[DrGER]

The "standard" 161 byte encoded copie_scr.sh script for launching SD card shell scripts on MMI 3G systems, while useful, doesn't take full advantage of its native QNX environment, namely, in how it determines the path to the calling SD card root/base directory. I've been using this frequently lately to look at various processes and file systems in our MMI 3G+ system, and found the "standard" copie_scr.sh lacking, particularly with regard to its behavior when other removable media is connected to the system.

Inspection of "pidin" shows that the script launcher process (proc_scriptlauncher) identifies correctly the mount path to the SD card in which the encoded copie_scr.sh script resides, for example:

  323657   24584 /bin/proc_scriptlauncher -i 30 -p /dev/shmem/copie_scr.sh
...
  966717  323657 ksh /dev/shmem/copie_scr.sh /mnt/sdcard10t12

and

  323657   24584 /bin/proc_scriptlauncher -i 30 -p /dev/shmem/copie_scr.sh
...
 1212477  323657 ksh /dev/shmem/copie_scr.sh /mnt/sdcard20t12

In the former case, the SD script is run from slot SD 1; in the latter, slot SD 2.

Thus, shell argument 1 to the encoded copie_scr.sh script contains the correct mount path to the SD card. Using this information about the calling process, we can include it in a new (encoded) copie_scr.sh script:

#!/bin/ksh
# 20220102 drger; MMI3G SD shell script launcher
export SDPATH=$1
export PATH=${SDPATH}/bin:$PATH
export SDLIB=${SDPATH}/lib
export SDVAR=${SDPATH}/var
export SWTRAIN="`cat /dev/shmem/sw_trainname.txt`"
mount -u $SDPATH
cd $SDPATH
exec ksh ./run.sh $SDPATH

Here, new exported environment variable SDPATH contains the value passed from the script launcher process as argument number 1 ($1). And while we're at it, we can prepend our SD card bin directory to the PATH, and add a new SWTRAIN environment variable using the contents of /dev/shmem/sw_trainname.txt (this is the MMI firmware version name) (along with a couple environment variables I use routinely in my MMI SD scripts: SDLIB and SDVAR).

Finally, the new encoded copie_scr.sh script launches our plain-text "run.sh" shell script with argument $SDPATH for completeness.

A ZIP archive of this new and improved copie_scr.sh SD card script launcher (and its source text) can be found HERE.

The size of this encoded copie_scr.sh file is 268 bytes and the md5sum is a18e6f7ebedc97b28f99cacb2ff87d4b. --g

[DrGER]

Some additional information on this topic:

The C source code to decrypt/encrypt the VAG Harman-Becker copie_scr.sh file comes from Github HERE.

The plain-text C source code:

#include <stdio.h>

unsigned int seed = 0x001be3ac;

unsigned int prng_rand() {
    unsigned int r1, r3, r0;

    r0 = seed;
    r1 = (seed >> 1) | (seed << 31);
    r3 = ((r1 >> 16) & 0xFF) + r1;
    r1 = ((r3 >> 8) & 0xFF) << 16;
    r3 -= r1;
    seed = r3;

    return r0;
}

int main(int argc, char *argv[]) {
    int c;

    prng_rand();

    c = getchar();
    while (c != EOF) {
        c ^= (prng_rand() & 0xFF);
        putchar(c);
        c = getchar();
    }
}

On most Unix/Linux systems, this can be compiled with gcc simply with: $ gcc -o copiescrio main.c

Simple shell redirection is used for input to & output from the executable copiescrio.

Thus, decrypting an existing copie_scr.sh file to plain-text: $ copiescrio < copie_src.sh > copie_scr.txt
And encrypting a plain-text source is the opposite: $ copiescrio < copie_scr.txt > copie_scr.sh